The field of this invention is that of devices providing for the ejection of a plurality of payload elements from the casing of a carrier shell.
Carrier shells are projectiles intended to transport a payload, then release it at a point in their trajectory.
The payload often contains a stack of several payload elements, for example submunitions.
French patent FR 2,363,077 describes one such type of carrier shell which contains a casing closed at one of its ends by a base and at the other by a head. A gas-generating pyrotechnic composition is placed inside the head, where it is ignited by a timer fuze to create gas pressure which acts on a piston. The thrust exerted by the piston on the stack of submunitions causes separation of the base and casing of the projectile, then ejection of the submunitions from the casing.
When a shell must eject a plurality of elements from its casing in this manner, the problem arises of collisions among these various elements after ejection.
Such collisions can lead to premature detonation in cases where the payload consists of submunitions. They can also result in disruptions in the trajectory of the payload elements, for example, by disrupting the opening of braking parachutes.
To prevent such collisions, French patent FR 2,363,077 proposes to create a piston which, under the action of gas pressure, can move towards the rear, pushing the payload elements, over only a short distance, the distance nevertheless being sufficient to shear off the screw thread connecting the casing and the base, and then to eject the base.
After ejection of the base, the piston is immobilized by a shoulder on the casing. However, the piston has an orifice which allows the gases of the ejecting pyrotechnic composition to pass towards the payload elements, which are thereby pushed towards the rear of the projectile after the piston stops.
The ejection velocity of the payload elements is reduced because of reduction in gas pressure produced by the orifice, and it is possible to regulate this velocity by adjusting the diameter of the orifice.
The principal disadvantage of such a device is that, in practice, it is not possible to control the ejection velocity of the payload elements, since ignition of the ejecting pyrotechnic composition violently pushes the piston, the stack of submunitions, and the base so that the latter can be ejected.
The energy transmitted is such that, in practice, although the piston is halted by the shoulder of the casing, the stack of submunitions continues on its way and is ultimately ejected from the shell at a velocity little different from the ejection velocity of the base.